This invention relates to a leather-wrapped steering wheel having the core thereof covered with a part made of semirigid urethane foam and the surface thereof finished with a leather wrap part.
FIG. 1 illustrates the stratal construction of a typical conventional leather-wrapped steering wheel.
The leather-wrapped steering wheel comprises a core 1, a core-covering part 2 made of semirigid urethane foam, a rubber layer 3 wrapped around the exterior of the core-covering part 2, and a leather wrap part 4 covering the rubber layer 3.
The semirigid urethane foam used in this construction has been generally produced by the reaction and injection molding of a urethane material which uses a polyether compound and/or a polymer polyol compound as the polyol moiety, a MDI compound as the polyisocyanate moiety, and a Freon (a proprietary fluorinated hydrocarbon product by DuPont) compound as the foaming agent.
The aforementioned semirigid urethane foam, however, is a foam possessing an integral-skin layer and exhibits high surface hardness of not less than 70 by the Askar C scale and low repulsion elasticity of not more than 15%. When the leather wrap part is formed as directly held in contact with the covering part made of the foam of the foregoing description, therefore, the feeling produced by the steering wheel on the hands taking hold of the steering wheel is not pleasant. Thus, it has been necessary to have a rubber layer (made of CR, for example) interposed between the covering part and the leather wrap part as described above, with the inevitable result that the number of steps of process for the manufacture of the steering wheel is increased and the weight of the steering wheel is proportionately increased.